- Oct 7, 2013
- 97FL, Florida, USA
When building the gosemer condor they neededtalking about tapered thickness spars - the Gossamer Condor or its offspring used an aluminum spar that was etched towards the tip. Cannot remember the etchant: caustic soda ??
I wish I had the actual report as well. But I got it first hand from the principal research Engineer doing the work. Since I cannot produce the proof I probably should have said something like "The US Air Force Labs purportedly..."I have read of some of the other above and beyond treatments from the bad old days, but not this one. I'd love to read about it if you have an idea of where to look for it...
That makes sense. I was within 70 miles of the Channel hop, but they didn't publicize it for obvious reasons, and I wasn't there. I COULD have been there <sigh>
I wonder how CF tubes, which can have the thickness varied from end to end as they're wound, would work in this application? Seems like not wasting structural weight in the tips, but keeping the tube diameter constant for assembly would be a win-win.On round tube spars in general: What VB said about structural efficiency; to be strong enough at the root, they're waaay overbuilt along the length to the tip. There's also the compromise of picking up a bit torsional rigidity (inefficiently), but wasting a lot of structure weight in the 'web' area of the spar. Offsetting that is the incredible ease of assembly when the spar is 'pre-assembled', and you can just slide the ribs onto the spar and jig them into alignment.
I don't know about the BD-4C, but the on the original, he didn't. With no loading, they were perfectly straight, tip to tip. The planes had slight anhedral when sitting on the ground due to the 'dead' weight of the wings & fuel, and very slight dihedral in flight due to lifting bending loads on the wings (think sailplane; not so much). I know some of the original wings had sump drains added to the outboard end of the wing tanks, so any water could be cleared.Interesting thread. How did Bede add dihedral to the centre section tube spar?